The present invention relates to colorants or dyes and, more specifically, to a decorative dye for use in various types of natural stone to alter the natural coloration of the stone.
A number of types of natural stone are often used as construction materials in residential and commercial buildings. The stone provides an aesthetically pleasing appearance and very durable component to the buildings in which it is used.
However, as the color of these types of stone varies depending upon the location of the quarry from which the stone is taken, and as most of these quarries are located abroad, once the desired color is selected, there usually is a large expense incurred by having the stone shipped to the construction site. Therefore, before choosing to utilize stone as a building material in the residential or commercial structure, the purchaser will normally make certain that the stone selected for the task exactly meets the specifications necessary for the shape, color, and quality of the stone.
The marble, granite, limestone, soapstone, and other types of natural stone utilized for this purpose have been formed in the earth over a period of many years. The formation process compresses many different mineral components together to form the stone and gives the stone a unique color pattern that varies even within the stone. In most applications, due to the shape necessary for the specific construction application, the stone will need to be cut and shaped to fit the application. When the stone is cut, the coloration of adjacent pieces of the stone may not exactly match one another due to the unique color pattern throughout the stone. Therefore, the stone may not fully present the desired aesthetically pleasing effect desired due to the variations in the coloration of adjacent pieces of the stone.
In this situation, the purchaser is normally forced to accept the color variations in the stone. Thus, purchasing natural stone for use as a decorative feature for a building entails a certain amount of risk regarding the appearance of the stone when the construction of the building is completed.
In the past, a number of processes have been used to attempt to lessen or modify color variations in different types of natural stone, thereby to make stone more desirable as a building material. One prior art process used to modify variations in the color of naturally-formed stone is to treat the stone under pressure with a mixture of an inorganic or organic pigment dissolved in a solvent. The pigment is applied to the surface of the stone and the pressure exerted on the dissolved pigment and the stone forces the pigment and solvent mixture deeply into the surface voids in the stone to provide a uniform color to the stone. However, the pigment used in this process is easily decomposed by heat or sunlight, and is also easily leached out of the surface voids by water.
An alternative process used for this purpose is one in which the stone is subjected to a very high temperature to expand the surface voids in the stone. A pigment is then applied to the heated stone. The pigment can more easily penetrate into the expanded voids. However, this process also is not very suitable for correcting color variations within the stone, as, due to the heat to which the stone was subjected, certain inherent properties of the stone are detrimentally affected. For example, the natural color of the stone deteriorates. Furthermore, certain physical properties, such as weather resistance, water resistance, and impact resistance, are also negatively affected.
Still another attempt to provide a suitable natural stone coloration process involved a process whereby a pigment blended with a thermosetting resin solution is impregnated into the voids in the stone. However, in this process, the pigment does not penetrate well into the stone, and provides only a surface coating that mars the natural beauty and smoothness of the polished surface of the stone.
A more recent process developed for the coloration of granite is disclosed in Cho, U.S. Pat. No. 4,695,487. In this patent, a pigment for coloring granite is formed by reacting a metal with a strong acid to obtain a metallic salt of the desired color for the granite. The metallic salt is then dissolved in a suitable solvent mixed with a small amount of a surfactant to allow the pigment to permeate into the surface voids and cracks within the granite. The granite and pigment solution are placed within a vacuum container that draws the pigment into the voids within the granite. Upon completion of the permeation of the pigment into the granite, the granite is then heated in a furnace under oxidizing atmospheric conditions to a temperature of between 250-300xc2x0 C. for 2-3 hours to increase the formation of metallic oxides within the numerous voids and cracks in the granite. The metallic oxides formed in the voids and cracks provide the desired color to the granite. Finally, to protect the newly formed metallic oxides within the granite, the granite is surface treated with a silicone oil to protect the metallic oxides formed within the voids, preventing the deterioration or removal of the metallic oxides.
While providing a reliable method for modifying color variations in granite, the method of the Cho patent does have significant shortcomings. First, the granite must be heated to very high temperatures in order for the process to be effective. In addition to being a very difficult and time consuming step, the step of heating the granite also greatly increases the cost of using the granite for decorative purposes. Second, as stated in the Cho patent, the process only works for granite, and not other types of porous stone, such as marble, limestone, and soapstone, which are also highly sought after types of decorative stone. Lastly, though the granite is treated with a silicone oil to prevent the deterioration of the color generated by the metal oxides formed by the process, should the oil layer fail for any reason, for example, if the stone become chipped or scratched, the colored metal oxides will quickly deteriorate and detract from the appearance of the colored, treated granite.
Because of the shortcomings of the prior art processes for coloring certain types of natural stones, there is a need for a colorant and process for coloring natural stone that is capable of permanently coloring the stone in an easy and cost effective manner without affecting any of the desired natural properties of the stone.
The present invention comprises a decorative dye colorant used to permanently or semi-permanently modify the color of various types of natural stone to provide aesthetically pleasing construction materials.
The dye colorant is able to inexpensively alter the color without affecting either the polished surface of the stone or any of the other inherent qualities of the stone.
The colorant includes a dye capable of matching or blending with the colors of natural stones. The dye used in the application is a powdered, solvent soluble dye that comes in a variety of colors. Specific amounts of the different color dyes available may be mixed to create the desired shade for the colorant used on the stone.
When mixed to the desired shade, the dye is dissolved in one of a number of suitable solvents to place the dye in a liquid form that may easily be applied to a polished natural stone surface. The solvents which may be used to dissolve the dye include a number of alcohols and ketones. Each effectively disperses the powered dye in the solvent, which acts as a carrier for the dye and allows the dye to easily penetrate into the pores in the stone surface. Once dissolved in the chosen solvent, the dissolved dye may also have a whitening pigment added to lighten the color of the dye as desired.
After being formed by mixing the dye with the solvent, the colorant may be applied to a polished surface of a natural stone in any conventional manner, similar to applying paint. When applied to the stone, the dissolved dye is carried by the solvent into the pores of the stone so that the dye, when the solvent is allowed to dry or evaporate out of the pores in the stone, sets within the pores beneath the polished surface of the stone.
After drying in the pores on the stone, the colorant becomes highly resistant to a variety of different substances. However, in this form, the colorant is not permanent and may be removed over time by extended contact with certain substances, such as bleach. This allows an individual to remove and change the color of the stone if desired. Also, if it is desired to permanently color the stone, a sealer can be applied to the surface of the stone over the colorant. The sealer also penetrates into pores of the stone and sets beneath the polished surface to provide an impervious layer between the polished surface and the colorant that prevents any staining or discoloration of the colorant.. The sealer can be applied to the.,.stone in any conventional manner, similar to the application of the dissolved dye.